The present invention relates to a fastening element, in particular a nut body, which has at one end a bearing surface for a washer held on the fastening element in a rotatable and captive manner. The present invention also relates to a washer having a contact surface for the bearing surface of a fastening element and to a fastening means which is formed from a fastening element and a washer.
A washer of the generic type has been disclosed by EP 1 091 135 A2. This washer has a washer body having at least two integrally formed retaining claws which can be folded around an encircling flange provided on the fastening element. In this way, the washer is held on the fastening element in a captive manner. German Utility Model DE 94 00 671 U1 describes a washer which, instead of retaining claws, has an annular web running around the washer body.
In the known embodiments of nut bodies having an encircling flange for holding the washer, the radial extent of the washer is limited. The outside diameter of the washer cannot be substantially greater than the diameter of the encircling flange. Otherwise, indentations would have to be made on the washer for producing the retaining claws, which on the one hand is expensive from the production point of view and on the other hand leads to instability of the washer. In addition, the thickness of the washer is also limited. The washer thickness must still allow the bending of the retaining claws or of the annular web around the flange.
Another possibility is to integrally form a retaining collar on the inner margin of the bearing surface of the fastening means, this retaining collar being beaded on the outside and thus holding a step in the washer. This configuration is described, for example, in DE 101 36 829 C1. In this case, however, in a hexagon nut, only a minimum bearing surface offset radially outward, i.e. asymmetrically, remains between nut body and washer. This leads to unfavorable transmission of force between washer and nut body. In addition, there is the risk of the bead margin of the retaining collar jamming on the step of the washer. In the case of a flanged nut, the retaining collar can be produced only with a considerable tool cost.